This two year Phase I project will combine the electrochemical biosensor technology with the unique silicon microneedle based ex-vivo monitoring technology, to produce low cost MEMS (MicroElectroMechanicalSystems) for continuous monitoring of blood alcohol levels. We propose to create mini-erosion of the skin with the silicon microneedles to obtain free flowing interstitial fluid (ISF). The alcohol level in the ISF will then be analyzed ex-vivo with the silicon based biosensor. The analyte in this work will be ethyl alcohol, but the technology is also applicable to many other analytes including continuous monitoring of glucose by diabetics. Diabetic glucose self-testing is currently the largest existing biosensor market opportunity. In the first year, electrochemical biosensors will be integrated into silicon microneedles to fabricate disposables for in vitro measurement. Issues related to continuous flow of fluids through the device will be evaluated using buffer solutions with serum proteins. The work of the second year will focus on extending the operating lifetime of these devices toward disposables for monitoring ethyl alcohol concentration continuously. Animal studies will be conducted to evaluate the strength of the microneedle for penetrating the stratum corneum as well as to establish feasibility of continuously monitoring ISF alcohol. Once the system is validated in animal models, human subject testing will be conducted under the supervision of Dr. Robert Swift at Brown University. A silicon biosensor microchip packaged with a telemetry chip to make a small button-like device which can be attached to the skin unobtrusively to measure alcohol concentration continuously and transmit this data will be the goal of a SBIR Phase II project. The strength of our approach lies in the ex-vivo monitoring of body fluid with a biosensor and thus avoid the problems associated with subcutaneously implanted in-vivo biosensors. The major challenges of subcutaneously implanted in-vivo biosensors are loss of sensitivity, fouling of the sensor over time and in-vivo calibration. We believe that by attempting to make the measurement outside the body with an integrated biosensor silicon microneedle could lead to the development of commercially viable continuous monitoring device.